This one’s impressive — Zen Bound originally started out as Zen Bondage, a physics game/sandbox where the goal was to wrap a rope around a 3D shape or object. The game has just recently been ported to the iPhone, and in the process has actually been improved — the graphics look sharper and the iPhone’s multitouch controls really add to the tactile experience.

As a “game,” it might be questionable — it looks like there’s a lot of fudging in terms of whether or not the rope has “covered” the object, and the scoring system itself is more or less tossed in as just a reason to get you to interact with the objects. But as an app, and a demonstration of the kinds of interactivity that can be exclusive to a device like the iPhone, it comes highly recommended.